The purpose of this project is to improve our understanding of ways in which drugs may alter centrally mediated neurotransmission and to develop better pharmacotherapies for neurological disorders. Topics currently under investigation include: (1) Factors regulating glutamic acid decarboxylase activity; (2) Effects of drugs on gamma-aminobutyric acid (GABA) synthesis; (3) Role of GABA-containing neurons in the regulation of dopaminergic function; (4) Neurotransmitter dysfunction in Huntington's chorea; and (5) Use of the stable isotope of oxygen (O18) to evaluate central monoamine metabolism in man.